As rare as consecutive pairs of Mint Of The United States At San Francisco silver ingots are to come by, consecutive trios are so much more rare, I can honestly say that before my collection, I know of no others. Certainly original purchasers were in possession of trios and more, (and may still secretly be), I am talking about those in circulation since the silver highs of 1980. Technically, these trios are not trifectas but putting three consecutively numbered ingots together sure feels like a win!
The greatest collection of US Government ingots previously assembled was that of Alan Bingel which according to a write up by Fred H (yes, that Fred H) contained some 66 examples. The Alan Bingel collection was sold by Heritage Auctions over a number of sessions beginning in 2005 and according to their auction archives, contained no consecutively numbered examples at all.
With my collection now of over 200 examples, consecutively numbered acquisitions are always a treasure. I have some 16 pairs and the trifectas pictured below: